The Ducting Dilemma: Why Air Ducts Often Create Greenhouse Climate Problems
For decades, air ducts have been the default solution for distributing air in greenhouses and grow rooms. The logic seems straightforward: if air isn’t reaching the plants, add tubes to push it there.
But once you understand how air actually behaves in high-density growing environments, a different picture emerges.
In many commercial greenhouses, more ducting does not lead to better climate uniformity. In fact, it often creates new problems – higher energy use, uneven humidity, sanitation risks, and lost light – while delivering fewer benefits than expected.
This article answers the most common questions growers ask about ducting and explains why air circulation, not air distribution, is the foundation of an effective greenhouse climate strategy.
Do I need air ducts to move dry air into the center of the canopy?
In most cases, no – if your air circulation is designed correctly.
Ducts work by forcing air through a confined space. That restriction creates static pressure, which means fans must work harder just to move the same volume of air. The result is air exiting the duct as high-velocity jets through perforated holes.
This causes two common problems:
- Plants directly in front of the holes experience excessive airflow and localized drying
- Just a short distance away, “dead pockets” of humid air remain untouched
The outcome is not uniform climate control, but uneven humidity across the canopy.
The alternative: full-volume air circulation.
A ductless circulation approach treats the greenhouse as a single air mass. High-volume airflow moves over the canopy and returns through the lower crop layers, creating a continuous 360° mixing loop. When air is constantly mixed, temperature and humidity equalize naturally- without needing tubes to “deliver” air to specific points.
How do air ducts affect greenhouse energy consumption?
They almost always increase it.
From a physics standpoint, pushing air through a duct requires more energy than moving air through an open space. Friction inside the tube reduces airflow efficiency, meaning fans must consume more electricity to achieve the same CFM.
Without ducts:
- Fans operate against lower resistance
- More air is moved per watt of electricity
- Overall system efficiency improves
In practical terms, removing ducting often results in lower energy use for the same – or better – climate performance.
Are air ducts a sanitation or maintenance risk?
Yes, and it’s one of the most overlooked issues.
Air ducts are:
- Dark
- Difficult to access
- Prone to condensation and dust buildup
These conditions make them ideal environments for mold spores and bacteria. If pathogens develop inside a duct, the airflow system can distribute them directly across the crop.
Maintenance is another challenge. Ducts are time-consuming to inspect and clean, and in many facilities, they are rarely cleaned thoroughly at all.
A ductless system eliminates these hidden contamination zones and simplifies sanitation across the facility.
Do air ducts block light in greenhouses?
They do – and the impact adds up.
Every object suspended above the crop creates shade. Long runs of ducting reduce light penetration, especially in high-wire crops and dense canopies. Even small percentages of light loss can translate into measurable yield reduction over an entire season.
By removing ductwork, greenhouses remain more open, brighter, and more uniform in light distribution – supporting both plant health and productivity.
Don’t ducts prevent microclimates?
In practice, ducts often create them.
As air travels through a duct, pressure drops along its length. This means:
- Strong airflow near the fan
- Weaker airflow toward the end of the tube
The result is variability of row-to-row and plant-to-plant. Instead of eliminating microclimates, ducting frequently reinforces them.
A ductless air circulation system continuously mixes the entire air volume, reducing localized differences and stabilizing humidity and temperature throughout the greenhouse.
Is ducting ever the right choice?
Sometimes – but only in specific situations.
Ducting can be useful in:
- Extremely narrow, low-ceiling facilities
- Vertical farming racks with tight airflow constraints
- Isolated zones where penetration is otherwise impossible
However, for the vast majority of commercial greenhouses and CEA facilities, ducting is an outdated habit– one that increases complexity, energy use, and maintenance without delivering better climate results.
Grower Takeaway
- You don’t need tubes to move air – you need airflow physics
- Ducts introduce resistance, shading, sanitation risks, and uneven distribution
- Climate uniformity comes from mixing the entire air volume, not directing air through holes
- In most greenhouses, ductless circulation is simpler, cleaner, and more energy efficient
At DryGair, years of greenhouse airflow analysis consistently show that treating the facility as one connected air mass leads to more stable humidity, fewer microclimates, and better overall growing conditions.
Want to understand how air really moves in your greenhouse?
If you’re considering ducting – or questioning whether your current system is working against you – start with airflow, not hardware.
Contact us for a climate consultation and discover whether ductless air circulation can simplify your greenhouse while improving performance.
